Smaller berries = better skin to fruit ratio = more tannin.(Warmer years commonly produce small berries.) Petit Verdot and Cabernet Sauvignon have a thick skin and can extract lots of tannins. Wine Tasting is fun so do not make it a complicated, scientific adventure. https://vibrant-mango-kvlmct.mystrikingly.com/blog/th-ng-th-c-r-u-hennessy-very-special-cognac-r-u-nh-p